||January 1, 2007
For developed countries, environmental focus has shifted from pollution prevention to sustainable development. It has been realized in the paving industry that preventative maintenance of existing roadways is the most financially effective use of available resources. Surface treatments applied to an existing pavement for preventative maintenance are the most significant application of polymer-modified asphalt emulsions. They are economical, easy to place, resist traffic abrasion and provide a long lasting waterproof cover over the underlying structure. Chip seal, slurry seal and microsurfacing are examples of asphalt emulsion-based surface treatment techniques. Researchers at the University of Florida have observed changes in pavement distress mechanisms which may be related to changes in historical tire type and structure. Newer radial tires, as opposed to bias-ply tires, induce high transverse contact stresses on pavements, resulting in high near-surface lateral stresses, which cause longitudinal surface cracking and near-surface rutting and shoving. These transverse contact stresses generated by radial tires could be confined within a preventative maintenance surface treatment layer. To prevent aggregate loss from the surface treatment, the asphalt binder holding the aggregate in place has to withstand excess transverse stresses generated by radial truck tires and snowplow operations. A new Dynamic Shear Rheometry (DSR) procedure was developed to evaluate potential reduction in the strength of the asphalt emulsion residue under repeated high-strain deformation. Results obtained with this procedure demonstrate advantages of the SBR latex polymer-modified asphalt emulsion for improved aggregate retention and early strength development.